1. Field of the Invention
The present invention relates to a semiconductor device in which a contacting point breakage of electrical bonding can be prevented, and to an image scanning unit utilizing the same and an image forming apparatus utilizing the same.
2. Description of the Prior Art
In the prior art technology a wireless bonding is well known, which has advantages in a higher densification of the contact pins and a miniaturization of the semiconductor device by means of connection of a large number of pins which are the contacting point of semiconductor chip onto the contacting points of a substrate when in comparison with the wire bonding in which the bonding pads on the semiconductor chip and the lead on the substrate are connected electrically with the metal fine line.
It is also well known that there is a face down bonding as one of the wireless bonding technology. This face down bonding is a method in that a bump or a beam lead is formed on a bonding pad of the semiconductor chip and the semiconductor chip is directly connected with its chip surface onto a conductor layer of the substrate by putting it with the chip surface down.
As a typical face down bonding method, there is a method called flip chip.
Because there is recently a requirement for miniaturization of semiconductor devices, it has been popular to achieve the semiconductor chip face down bonding with the substrate as a method for further miniaturization of a package of the semiconductor chip and the substrate.
When a semiconductor chip is achieved a face down bonding onto a substrate, it is also well known that a means is employed to prevent a breakage in the circuit, for example, caused by the thermal expansion by means that an adhesive material is used (as a sealing compound) between the semiconductor chip and the substrate in order to prevent an occurrence of a electrical breakage (at contacting point) in a circuit which is caused by a difference in the coefficients of thermal expansion between the semiconductor chip and the substrate.
The thermal expansion generally becomes large in proportion to a difference in temperature and a length of the object. An amount of the expansion is dependent on a coefficient which is different in accordance with the material of object, namely, a coefficient of thermal expansion. Because of the above described reason in an object with longer length such as a line CCD which is used in a copy machine, facsimile, scanner and so on, an amount of the thermal expansion especially along a longer direction becomes extremely large.
Due to this fact even when the adhesive material (sealing compound) is used between the semiconductor chip and the substrate as described above, the electrical contacting point are relatively moved because the difference between the amount of thermal expansion is too large. As a result of this, there was a problem that the contacting point between the semiconductor chip and the substrate was broken.
In the past a semiconductor chip has been well known in that the semiconductor chip and the substrate were covered with a resin which was disclosed in the Japanese Laid Open Patent Hei 05-218230. In this semiconductor chip a semiconductor chip which is mounted with a flip chip structure is covered with a resin, However, there is a problem in the method disclosed in the Japanese Laid Open Patent Hei 06-218230 that the thermal expansion is accelerated because even a back surface of the functional surface of semiconductor chip is also covered with the resin, and thereby a place from which heat generated by high speed driving of the semiconductor chip is radiated, is also covered with resin too, the method can not prevent effectively the breakage of contacting point by the thermal expansion. Especially a significant effect is shown in the semiconductor chip with longer length.
Because of the above described situation an object of the present invention is to provide a semiconductor chip in which a contacting point breakage of electrical bonding can be prevented, and to provide an image scanning unit utilizing the same and an image forming apparatus utilizing the same.
Another object of the present invention is to provide a semiconductor chip in which a curvature of the semiconductor chip with the optical functional surface by the thermal expansion can be prevented to forbid an occurrence of out of focus, and to provide an image scanning unit utilizing the same and an image forming apparatus utilizing the same.
To achieve the above described objects the present invention provides a semiconductor device including: a semiconductor chip which has a functional surface; a power supplying means which is connected to the functional surface; and a substrate which supports the semiconductor chip and the power supplying means, wherein the semiconductor chip is fixed on the substrate at portion other than a connecting potion between the functional surface and the power supplying means.
A 1st feature of the present invention is a semiconductor device including an assembly in which a semiconductor chip having a functional surface and a power supplying means are electrically connected at the functional surface, characterized by that the assembly is disposed on a substrate with the power supplying means side being the substrate side, and the substrate and the assembly are fixed together at a portion other than the power supplying means portion.
In this structure a pinched portion of the power supplying means is free from the movement of substrate because the substrate and the assembly are fixed through portions other than power supplying means when the substrate and the semiconductor chip make an expansion and contraction in different amount under an influence of heat. Accordingly any stress does not affect on the contacting portion between the power supplying means and the semiconductor chip thereby a breakage of the assembled portion can be prevented.
A 2nd feature of the present invention is a semiconductor device including an assembly in which a semiconductor chip having a functional surface at a front surface and a power supplying means are electrically connected at the functional surface, characterized by that the assembly is disposed on a substrate with the power supplying means side being the substrate side, the power supplying means has a pinched portion between the semiconductor device and the substrate, and the substrate and the semiconductor device are fixed together at a portion other than the pinched portion.
In this structure a pinched portion of the power supplying means is free from the movement of substrate because at least pinched portion of the power supplying means moves integratedly with the semiconductor chip and the pinched portion is not fixed on the substrate when the substrate and the semiconductor chip make an expansion and contraction in different amount under an influence of heat. Accordingly any stress does not affect on the contacting portion between the power supplying means and the semiconductor chip thereby a breakage of the assembled portion can be prevented.
A 3rd feature of the present invention is the semiconductor device according to the 2nd feature and characterized by that an adhesive material which adheres the semiconductor chip and the substrate to fix, is filled at a space between the substrate and the functional surface of the semiconductor chip In this structure in addition to an action by the above described 2nd feature, because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
A 4th feature of the present invention is the semiconductor device according to the above described 2nd feature and characterized by that the adhesive material which adheres the semiconductor chip and the substrate to fix, adheres them with contacting the substrate and a back surface of the semiconductor chip. In this structure in addition to an action by the above described 2nd feature, because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
And at the same time the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface).
A 5th feature of the present invention is the semiconductor device according to the above described 2nd feature and characterized by that the adhesive material which adheres the semiconductor chip and the substrate to fix, adheres them on at least one surface other than both of a front surface and the back surface of the semiconductor chip. In this structure in addition to an action by the above described 2nd feature, because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
And at the same time the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface).
A 6th feature of the present invention is the semiconductor device according to the above described 5th feature and characterized by that the adhesive material is covered with adhesive material which has been cured. In this structure in addition to the action by the above described 5th feature a flowing out of the adhesive material is cleared and thereby it is prevented that the flown out adhesive material enters into a space between the functional surface of the semiconductor chip and the substrate. Also the initial shape of the adhesive material is kept and thereby disposition of the adhesive material becomes easier.
A 7th feature of the present invention is the semiconductor device according to the above described 6th feature and characterized by that a cross section of the adhesive material is a circular. In this structure in addition to the action by the above described 6th feature strength can be given to the adhesive material against to the internal and external pressure before the adhesive material is cured.
An 8th feature of the present invention is the semiconductor device according to the above described the 6th feature and characterized by that a cross section of the adhesive material is a polygonal. In this structure the adhesive strength can be made higher because an adhering area between the adhesive material and the semiconductor chip and the substrate can be took wider.
A 9th feature of the present invention is the semiconductor device according to the above described the 5th feature and characterized by that the adhesive material is held by an adhesive material holding means. In this structure in addition to the action by the above described 5th feature the adhesive material would not wraparound between the functional surface of semiconductor and the substrate because the flowing out of adhesive material can be prevented effectively even when the adhesive material with low viscosity is utilized. According to this fact the adhesive material with low viscosity can be used as the adhesive material.
A 10th feature of the present invention is the semiconductor device according to the above described 9th feature and characterized by that the adhesive material holding means is made of a sponge like material. In this structure the adhesive material in the supporting body can be operated with a negative pressure and by this negative pressure the adhesive material can be supported in the body.
A 11th feature of the present invention is the semiconductor device according to the above described 9th feature and characterized by that the adhesive material holding means is made of an aggregated body of fibers. In this structure the adhesive material holding means is made of the aggregated body of fibers to hold the adhesive material.
A 12th feature of the present invention is the semiconductor device according to any one of the above described 9th to 11th feature and characterized by that the adhesive material holding means has a light transparent property. In this structure because the light can be irradiated onto all the holding adhesive material through the adhesive material holding means a photo curing type adhesive material can be usable.
A 13th feature of the present invention is the semiconductor device according to any one of the above described 2nd, 4th to 12th feature and characterized by that the substrate is made of a light transparent material, the semiconductor chip has an optical functional surface and a space is formed between the optical functional surface and the light transparent substrate as a light incident space. In this structure in addition to the action by the above described 2nd, 4th to 12th feature because the adhesive material is not disposed in the light path area, the light incident to (or going out from) the semiconductor chip is not blocked by the bubble or impurities in the adhesive material, thereby the problem that the performance of semiconductor chip is deteriorated would not occur.
A 14th feature of the present invention is the semiconductor device according to any one of the above described 3rd to 13th feature and characterized by that the adhesive material is a photo curing type adhesive material. In this structure the semiconductor chip and the substrate can be adhered to fix without any discrepancy of holding position due to thermal expansion because a rise in temperature would not almost occur when the adhesive material is cured by a light. Also it does never happen that a residual stress influenced by a temperature change in the adhering process.
A 15th feature of the present invention is the semiconductor device according to the above described 3rd to 13th feature and characterized by that the adhesive material is a heat curing type adhesive material having a curing temperature which is lower than a temperature that breaks a junction of the assembly. In this structure even in the area to which curing light cannot be reached, adhesive material can be cured by the heat curing type adhesive material.
And because the curing temperature for the heat curing type adhesive material is selected at a predetermined temperature that is lower than a temperature that breaks the conjunction of the assembly which electrically connects the semiconductor chip 2 with the wiring portion 5 of the substrate 1, the substrate 1 and the semiconductor chip 2 can be connected and fixed with maintaining a reliability of the electrical conjunction without occurrence of breakage of the conjunction.
A 16th feature of the present invention is the semiconductor device according to the above described 2nd feature and further including a fixing means which fixes the assembly on the substrate, characterized by that the fixing means has a heat radiating means. In this structure in addition to the action by the above described 2nd feature the generated heat in the semiconductor chip can be effectively released to environment. Also there is no need to add further parts for heat releasing.
A 17th feature of the present invention is a semiconductor device including an assembly in which a semiconductor chip having a functional surface at a front surface and a power supplying means are electrically connected at the functional surface, characterized by that the assembly is disposed on a substrate with the power supplying means side being the substrate side, the power supplying means has a slidably pinched portion between the semiconductor device and the substrate, the substrate and the semiconductor device are fixed together at a portion other than the pinched portion and a heat radiating means is disposed at a back side of the semiconductor chip.
In this structure a pinched portion of the power supplying means is free from the movement of substrate because at least pinched portion of the power supplying means moves integratedly with the semiconductor chip and the pinched portion is not fixed on the substrate when the substrate and the semiconductor chip make an expansion and contraction in different amount under an influence of heat. Accordingly any stress does not affect on the contacting portion between the power supplying means and the semiconductor chip thereby a breakage of the assembled portion can be prevented and furthermore because the heat radiating means is disposed heat generated from the semiconductor chip can be released effectively to environment and thereby deformation of the semiconductor chip can be prevented.
A 18th feature of the present invention is the semiconductor device according to the above described 17th feature and characterized by that an adhesive material which fixes the semiconductor chip and the substrate is filled at a space between the substrate and the functional surface of the semiconductor chip. In this structure in addition to the action by the above described 17th feature because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
A 19th feature of the present invention is the semiconductor device according to the above described 17th feature and characterized by that the adhesive material which adheres the semiconductor chip and the substrate to fix, adheres them with contacting the substrate and a back surface of the semiconductor chip. In this structure in addition to the action by the above described 17th feature.
In this structure in addition to the action by the above described 17th feature because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
And at the same time the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface).
A 20th feature of the present invention is the semiconductor device according to the above described 17th feature and characterized by that the adhesive material which adheres the semiconductor chip and the substrate to fix, adheres them on at least one surface other than both of a front surface and the back surface of the semiconductor chip.
In this structure in addition to the action by the above described 17th feature because the stress caused by the thermal expansion and contraction between the semiconductor chip and the substrate is not concentrated to specific region and the stress is absorbed in entire structure, thereby the local breakage of semiconductor chip and substrate can be prevented.
Also the adhesive material 3 is made not to contact with the functional surface 2a (optical functional surface 20a) of the semiconductor, thereby the problem that the adhesive material becomes an invisible electrical circuit and the semiconductor device can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance, or the problem that the adhesive materials happens to inundate to the accepting surface (or the light emitting surface) of the device and block off the light path when the semiconductor chip is utilized as the optical device, are solved.
A 21st feature of the present invention is the semiconductor device according to the above described 20th feature and characterized by that the adhesive material is covered with adhesive material which has been cured. In this structure in addition to the above described feature a flowing out of the adhesive material is cleared and thereby it is prevented that the flown out adhesive material enters into a space between the functional surface of the semiconductor chip and the substrate. Also the initial shape of the adhesive material is kept and thereby disposition of the adhesive material becomes easier.
A 22nd feature of the present invention is the semiconductor device according to the above described 21st feature and characterized by that a cross section of the adhesive material is a circular. In this structure in addition to the action by above described 21st feature strength can be given to the adhesive material against to the internal and external pressure before the adhesive material is cured.
A 23rd feature of the present invention is the semiconductor device according to the above described 21st feature and characterized by that a cross section of the adhesive material is a polygonal. In this structure in addition to the action by above described 21st feature the adhesive strength can be made higher because an adhering area between the adhesive material and the semiconductor chip and the substrate can be took wider.
A 24th feature of the present invention is the semiconductor device according to the above described 20th feature and characterized by that the adhesive material is held by an adhesive material holding means. In this structure in addition to the action by above described 20th feature the adhesive material would not wraparound between the functional surface of semiconductor and the substrate because the flowing out of adhesive material can be prevented effectively even when the adhesive material with low viscosity is utilized. According to this fact the adhesive material with low viscosity can be used as the adhesive material.
A 25th feature of the present invention is the semiconductor device according to the above described 24th feature and characterized by that the adhesive material holding means is made of a sponge like material. In this structure the adhesive material in the supporting body can be operated with a negative pressure and by this negative pressure the adhesive material can be supported in the body.
A 26th feature of the present invention is the semiconductor device according to the above described 24th feature and characterized by that the adhesive material holding means is made of an aggregated body of fibers. In this structure the adhesive material holding means is made of the aggregated body of fibers to bold the adhesive material.
A 27th feature of the present invention is the semiconductor device according to any one of the above described 24th to 26th feature and characterized by that the adhesive material holding means has a light transparent property. In this structure because the light can be irradiated onto all the holding adhesive material through the adhesive material holding means a photo curing type adhesive material can be usable.
A 28th feature of the present invention is the semiconductor device according to any one of the above described 24th to 26th feature and characterized by that the substrate is made of a light transparent material, the semiconductor chip has an optical functional surface and a space is formed between the optical functional surface and the light transparent substrate as a light incident space. In this structure in addition to the above action by above described 17th, 19th-27th feature because the adhesive material is not disposed in the light path area, the light incident to (or going out from) the semiconductor chip is blocked by the bubble or impurities in the adhesive material, thereby the problem that the performance of semiconductor chip is deteriorated would not occur.
A 29th feature of the present invention is the semiconductor device according to any one of the above described 17th to 28th feature and characterized by that the adhesive material is a photo curing type adhesive material. In this structure the semiconductor chip and the substrate can be adhered to fix without any discrepancy of holding position due to thermal expansion because a rise in temperature would not almost occur when the adhesive material is cured by a light. Also it does never happen that a residual stress influenced by a temperature change in the adhering process.
A 30th feature of the present invention is the semiconductor device according to any one of the above described 17th to 28th feature and characterized by that the adhesive material is a heat curing type adhesive material having a curing temperature which is lower than a temperature that breaks a junction of the assembly. In this structure even in the area to which curing light cannot be irradiated, adhesive material can be cured by the heat curing type adhesive material.
A 31st feature of the present invention is the semiconductor device according to the above described 17th feature and further including a fixing means which fixes the assembly on the substrate, characterized by that the fixing means has a heat radiating means. In this structure in addition to the action by above described 17th feature, the generated heat in the semiconductor chip can be effectively released to environment. Also there is no need to add further parts for heat releasing.
A 32nd feature of the present invention is the semiconductor device according to any one of the above described 17th to 30th feature and characterized by that the heat radiating means is made of an elastic member which performs an elastic deformation according to a thermal deformation of the semiconductor chip along a direction of the functional surface of the semiconductor chip. In this structure in addition to the above described 17th-30th feature, the heat radiating means would not regulate against the expansion and the contraction by heat and thereby the expansion and the contraction of the heat radiating means does not effect on the semiconductor chip. By this arrangement the semiconductor chip and the substrate are made to be free from the thermal stress other than caused by themselves, and thereby they are free from deformation by an external force.
A 33rd feature of the present invention is the semiconductor device according to the above described 32nd feature and characterized by that the elastic member is a wave like member which is formed in a wave like shape. In this structure in addition to the above described 32nd feature the heat radiating means can have the elasticity along an expansion and a contraction direction of the semiconductor chip even when the heat radiating means are made of a hard material.
A 34th feature of the present invention is the semiconductor device according to the above described 32nd feature and characterized by that the elastic member is a spiral like member which is formed in a spiral shape. In this structure in addition to the action by above described 32nd feature the heat radiating means can have the elasticity along an expansion and a contraction direction of the semiconductor chip even when the heat radiating means are made of a hard material.
A 35th feature of the present invention is the semiconductor device according to any one of the above described 17th to 31st feature and characterized by that the heat radiating means is a wire like member which is formed in a wire like shape. In this structure in addition to the action by above described 17th-31st feature to the expansion or the contraction of the semiconductor chip which is caused by heat, the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device.
A 36th feature of the present invention is the semiconductor device according to any one of the above described 17th to 31st feature and characterized by that the heat radiating means is a spike like member which is formed in a spike like shape. In this structure in addition to the Acton by above described 17th-31st feature to the expansion or the contraction of the semiconductor chip which is caused by heat, the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device.
A 37th feature of the present invention is the semiconductor device according to any one of the above described 17th to 31st feature and characterized by that the heat radiating means is a spherical member which is formed in a spherical shape. In this structure in addition to the action by above described 17th-31st feature to the expansion or the contraction of the semiconductor chip which is caused by heat, the heat radiating means would not regulate to the expansion and the contraction along the direction of the expansion and the contraction because the heat radiating means is made to have a smaller contacting area space contacting with the semiconductor device.
A 38th feature of the present invention is the semiconductor device according to any one of the above described 17th to 31st feature and characterized by that the heat radiating means is made of a material which has a thermal expansion coefficient similar to that of the semiconductor device. In this structure in addition to the action by above described 17th-31st feature because the heat radiating means which has the thermal expansion coefficient near to that of the semiconductor device, the heat radiating means expands and contracts equally corresponding to the expansion and contract of the semiconductor device along the longer direction which is caused by a heat generation. By this arrangement the heat radiating means would not influence to the expansion and the contraction of the semiconductor device. And at the same time the expansion and the contraction of the heat radiating means would not influence on the semiconductor chip. Because of this fact the heat radiating means would not give a stress to the semiconductor device and it can increase the heat releasing effect.
A 39th feature of the present invention is the semiconductor device according to any one of the above described 17th to 28th feature and characterized by that the semiconductor chip is a solid state image forming device. In this structure in addition to the action by above described 13th-28th feature because the adhesive material is not disposed in the light path area, the light incident to (or going out from) the semiconductor chip is blocked by the bubble or impurities in the adhesive material, thereby the problem that the performance of semiconductor chip is deteriorated would not occur.
A 40th feature of the present invention is an image scanning unit characterized by including the semiconductor device. In this structure because the contacted portion between the solid state image forming device and the power supplying means is made free from breakage by heat and the incident light to the solid state image forming device is not blocked off and the performance of solid state image forming device can be carried out sufficiently, there is no possibility of occurrence of error in reading the image data and thereby the image scanning unit with high reliability can be provided.
A 41st feature of the present invention is an image forming apparatus characterized by including the image scanning unit. In this structure because the contacted portion between the solid state image forming device and the power supplying means is made free from breakage by heat and the performance of solid state image forming device can be carried out sufficiently, there is no possibility of occurrence of error in reading the image data and because the image forming apparatus includes the image forming unit which can carry out the image forming with high reliability, the apparatus can form electrostatic latent image with high accuracy thereby there is no possibility of occurrence of error in reading the image of the manuscript.